Im in the process of treating my tank for BGA with erythromycin. Alot of my BGA is under my pool filter sand substrate. Im just wondering if I need to inject the meds into the sand or if the meds will get into my substrate.
It should penetrate the sand since water also flows through your sand as well. If you're not feeling assured, you can fill a syringe (1-2mL/gallon) with hydrogen peroxide and apply it directly to the BGA. The fun thing about peroxide is that it makes stuff float.